Fig. 1

Neutrophils help CTCs survive, proliferate, and metastasize. Interactions with neutrophils enhance the survival, proliferation, and metastasis of circulating tumor cells (CTCs) in the bloodstream. Expression of vascular cell adhesion molecule 1 (VCAM1) in cancer cells mediates the formation of CTC–neutrophil clusters, through binding to specific integrins such as α3β1 integrin on neutrophils. CTCs also express G-CSF to stimulate the pro-tumor functions of neutrophils. In turn, neutrophils clustered with CTCs secrete cytokines such as IL-1β and IL-6, which promote CTC survival and proliferation through increased expression of Ki67